British Prime Minister David Cameron concedes that Scotland had what it takes to be an independent nation, but said it currently enjoyed ‘‘the best of both worlds‘‘, imploring it not to break the United Kingdom apart.

Stepping up his government’s campaign to hold Britain together ahead of an independence referendum expected next year, Cameron urged Scotland not to sever a union with England that dates back 306 years.

‘‘Put simply: Britain works. Britain works well. Why break it?’’ he wrote in an article published in Scottish newspapers.

‘‘This big question is for Scotland to decide. But the answer matters to all of our United Kingdom. Scotland is better off in Britain. We’re all better off together and poorer apart.’’

Cameron’s political future and historic legacy are on the line. He has pledged to contest the next British general election in 2015 and his own Conservative party would never forgive him if he presided over the break-up of a United Kingdom comprising England, Scotland, Wales and Northern Ireland.

London’s main parties are campaigning jointly against independence, knowing that Alex Salmond’s Scottish National Party (SNP) is an astute and highly motivated political machine that will spare no effort to win a vote on its flagship policy.

Tapping into an emotive cocktail of historical rivalry, opposing political tastes, and a perception that the British parliament in London does not nurture Scotland’s national interests, the ‘‘Yes Scotland’’ campaign wants independence to be a reality by 2016.

PROBLEMS OF BREAK-UP

Scottish secession could create serious problems for the remainder of the United Kingdom.

Britain’s Trident nuclear submarine fleet is based in Scotland, revenues from Scottish North Sea oil remain important to its coffers, and analysts said Britain would find it harder to maintain its voice in international bodies such as the UN Security Council as well as in European Union decision-making.

The SNP published a document this month suggesting the transition arrangements could be made within 16 months, and that Independence Day for Scotland could come in March 2016, a timetable opponents dismissed as unrealistic.

Opinion polls suggest support for independence has stalled. The latest put it at 32 per cent and opposition at 47 per cent. But Cameron and politicians from other parties remain nervous.

The government is expected to release the first of many policy papers on Scottish independence on Monday, analysing the legal and constitutional implications of a ‘‘Yes’’ vote.

One of the central planks of Cameron’s argument is that Scotland already enjoys a high degree of autonomy through its own parliament, and he has hinted that it would be able to repatriate even more powers if it rejected full independence.

‘‘I have no time for those who say there is no way Scotland could go it alone. I know first-hand the contribution Scotland and Scots make to Britain’s success — so for me there’s no question about whether Scotland could be an independent nation,’’ Cameron writes.

‘‘We want you to scrutinise, challenge and form your own opinion. This must not be a leap in the dark, but a decision made in the light of day.’’